This invention relates to a marine propulsion system, and more particularly to a fuel pump arrangement for a marine propulsion system.
In a marine propulsion system in which an internal combustion engine is mounted in the interior of a boat, such as a stern drive or inboard system, it is common practice to employ a mechanical diaphragm-type fuel pump to supply fuel to the engine carburetor or fuel injection system. This type of fuel pump typically includes a reciprocating actuator arm interconnected with a diaphragm pumping member. In the past, the fuel pump has been mounted directly to a mounting surface provided on the engine block, with an opening being formed in the engine block at the fuel pump mounting surface. The fuel pump was mounted to the mounting surface such that the actuator arm extended through the opening. A fuel pump push rod was mounted so as to extend between the actuator arm and a cam member mounted to the engine cam shaft. Rotation of the engine cam shaft resulted in reciprocating movement of the push rod, and thereby reciprocating movement of the fuel pump actuator arm, to operate the fuel pump.
With some engine models, the fuel pump mounting surface has been eliminated. Accordingly, it has become necessary to either use a different type of fuel pump, e.g. an electrical fuel pump, or to provide an alternate arrangement for driving a mechanical fuel pump. In a marine application, a mechanical fuel pump provides certain advantages over an electric fuel pump. For example, a mechanical-type pump does not require a return line between the pump and the fuel tank, as required by an electric pump, which can lead to fuel vapor problems as well as problems in pressure fluctuation. In addition, an electric pump requires electrical leads, and it is advantageous to reduce electrical leads in a marine application to the greatest extent possible.
Accordingly, it is an object of the present invention to provide an arrangement for operating a mechanical-type fuel pump, in which the fuel pump is not mounted to the engine block. It is another object of the invention to provide a simple and efficient fuel pump operating system, involving minor modifications to existing engine components.
In accordance with the invention, a mechanical-type fuel pump is located adjacent a water pump which is mounted to the engine for supplying water to the engine cooling system. The water pump includes a housing, an impeller, and an input shaft rotatably mounted to the housing and driven in response to operation of the engine. The water pump input shaft extends exteriorly from the housing, and a driven pulley is mounted to the end of the input shaft. The driven pulley is driven by a belt which is trained around the drive pulley mounted to the engine crankshift, so that the water pump input shaft is driven by the drive belt through the engine crankshaft. The fuel pump is driven in response to rotation of the water pump input shaft. The fuel pump includes an actuator arm which is maintained in engagement with a cam surface provided on the water pump input shaft, so that rotation of the input shaft results in reciprocating movement of the fuel pump actuator arm. The cam surface is provided by a cam member mounted to the water pump input shaft.
With the arrangement of the invention, only minor modifications to the water pump housing are necessary to accommodate mounting of the fuel pump thereto. In addition, the water pump input shaft is modified only slightly by mounting of the cam member to the shaft. In most other respects, the water pump is substantially identical to a water pump previously employed in this type of marine propulsion system. Accordingly, the invention requires modifications to the water pump which are few in number and relatively minor in nature.
The invention further contemplates a method of operating a fuel pump, substantially in accordance with the foregoing summary.
Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings.